Fan construction

ABSTRACT

A fan construction including a fan housing, a door pivotally mounted on said housing and carrying a fan wheel and a motor drive therefor, a first frame on said housing, a second frame on said door, fastener means for selectively securing said first and second frames together with said second frame bearing on said first frame when said fan wheel is in operating position in said housing, a roller mounted on a lever on said second frame, and means for causing the roller to be brought into engagement with said first frame to support the weight of said door and move said second frame away from said first frame so as to permit said door to be opened by rolling it on said roller.

United States Patent Habdo et al.

1 Mar. 18, 1975 1 FAN CONSTRUCTION [75] Inventors: Robert T. Habdo, Tonawanda;

William P. Burger, Buffalo, both of NY.

[73] Assignee: Buffalo Forge Company, Buffalo,

[22] Filed: Apr. 18, 1973 [21] Appl. No.: 352,316

[52] US. Cl. 417/360, 417/361 [51] Int. Cl. F041) 17/00 [58] Field of Search 417/360, 361; 415/201; 49/396 [56] References Cited UNITED STATES PATENTS 1,462,708 7/1923 Layne 417/360 X 1,935,538 11/1933 Baumann 417/423 R 3,281,992 1 1/1966 Morrison 49/396 3,475,861 1 1/1969 Hillseth 49/396 X FOREIGN PATENTS OR APPLlCATlONS 407.268 3/1934 Great Britain 417/360 175,368 5/1961 Sweden 417/360 Primary E.taminerC. .1. Husar Assistant Examiner-Gregory Paul LaPointe Attorney, Agent, or Firm-Joseph P. Gastel [57] ABSTRACT A fan construction including a fan housing, a door pivotally mounted on said housing and carrying a fan wheel and a motor drive therefor, a first frame on said housing, a second frame on said door, fastener means for selectively securing said first and second frames together with said second frame bearing on said first frame when said fan wheel is in operating position in said housing, a roller mounted on a lever on said second frame, and means for causing the roller to be brought into engagement with said first frame to support the weight of said door and move said second frame away from said first frame so as to permit said door to be opened by rolling it on said roller.

9 Claims, 18 Drawing Figures PATENTEI] NARI 8 I975 saw 7 9f 1 FAN CONSTRUCTION The present invention relates to an improved fan construction for permitting access into a heavy duty industrial fan for cleaning or repair.

By way of background, in the past heavy duty industrial fans were generally fabricated with the fan and motor assembly permanently mounted on the housing. Therefore, if the fan required cleaning or repair, it had to be disassembled or a man had to crawl into the fan through an access door. Both procedures were unsatisfactory inasmuch as they were excessively time consuming. Furthermore in the event-that the fan was not disassembled for cleaning or repair, it was difficult to obtain complete access to all of the parts when they were in place within the housing. It is with overcoming the foregoing deficiencies of prior fan constructions that the present invention is concerned.

It is accordingly the primary object of the present invention to provide an improved fan construction which permits the fan wheel to be swung out of the fan housing in a relatively simple and efficient manner for cleaning or repair of the fan wheel or the housing and which provides a rigid supporting structure for the fan wheel and its drive mechanism both when the fan wheel is in operating position within the housing and when it is swung out from the housing.

Another object of the present invention is to provide an improved mounting structure associated with a heavy duty industrial fan which permits the fan wheel and its motor drive which are relatively heavy to be capable of being moved to a position with the fan wheel outside of the fan housing with relatively little force because of the manner in which they are mounted on the housing.

A further object of the present invention is to provide an improved heavy duty fan construction in which the act of opening the door of the housing, on which the fan wheel and its associated drive structure are mounted, also serves to move the fan wheel out of axial overlapping engagement with an inlet bell of the fan so as to permit the fan wheel to be swung outwardly from the housing without interference with the inlet bell. Other objects and attendant advantages of the present invention will readily be perceived hereafter.

The improved fan construction of the present invention comprises a fan housing, a door, pivot means pivotally mounting said door on said fan housing. a fan wheel journalled on said door for rotation within said fan housing when said door is closed, means mounted on said door for driving said fan wheel, a first rigid frame section fixed to said fan housing, a second rigid frame section fixed to said door and bearing on said first frame section, fastener means for selectively rigidly securing said first and second rigid frame sections to each other when said door is closed to thereby securely mount said fan and said means for rotating said fan relative to saidhousing, roller means on said second rigid frame section, and means for terminating said bearing relationship between said first and second frame sections and causing the weight of said door to be shifted to said first frame section through said roller means whereby said door may be opened by rolling it on said roller means.

The various aspects of the present invention will be more fully understood when the following portions of the specification are read in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of one embodiment of the improved fan construction of the present invention;

FIG. 2 is an end elevational view taken from the left of FIG. I;

FIG. 3 is a plan view of the fan shown in FIG. 2 but with the door in an open position;

FIG. 4 is a fragmentary cross sectional view taken substantially along line 4-4 of FIG. 1 and showing the details of the hinge and latching structure of the door;

FIG. 5 is a fragmentary cross sectional view taken substantially along line 5-5 of FIG. 2 and showing the interrelationship between the rigid frame section on the door and the rigid frame section on the housing and related structure;

FIG. 6 is a fragmentary cross sectional view taken substantially along line 66 of FIG. 5 and showing the wheel on the door frame section in engagement with the track;

FIG. 7 is a fragmentary cross sectional view taken substantially along line 7-7 of FIG. 5 and showing the fastener bolts for securing the door frame section and the housing frame section in tied-together relationship;

FIG. 8 is a side elevational view of another embodiment of the present invention showing the door and its associated mounting structure used in conjunction with an in-line centrifugal fan having an overlapping axial relationship between the inlet bell and the fan wheel;

FIG. 9 is a side elevational view of the fan structure taken from the right of FIG. 8;

FIG. 10 is a plan view of the fan construction shown in FIG. 9;

FIG. 11 is a fragmentary cross sectional view taken substantially along the line 11-11 of FIG. 9 and showing primarily the frame section associated with the fan housing;

FIG. 12 is a side elevational view similar to FIG. 9 but showing the housing door in an open position;

FIG. 13 is a fragmentary cross sectional view taken substantially along line l3l3 of FIG. 9 and showing the constructional details of the wheel on the door frame section and the fastener means for locking the door frame section and the housing frame section together;

FIG. 14 is a fragmentary cross sectional view taken substantially along line l4-l4 of FIG. 10 and showing the screw for actuating the wheel lowering lever;

FIG. I5 is a cross sectional view taken substantially along line l5-I5 of FIG. 9 and showing the door in an open position;

FIG. 16 is an enlarged fragmentary cross sectional view taken substantially along line 15-15 of FIG. 9 and showing the details of the door hinge structure;

FIG. 17 is an enlarged fragmentary cross sectional view taken substantially along line l5lS of FIG. 9 and showing the details of the bolts for locking the door in a closed position; and

FIG. I8 is a fragmentary enlarged view. partially in cross section showing the axial overlapping relationship between the inlet bell and the fan wheel.

The improved centrifugal fan construction I0 of the present invention, as shown in FIGS. [-7, includes a fan housing II which includes opposed side walls 12 and I3, effectively mounting fan scroll 25 therebetween. The ends of side wall 13 are bent outwardly to form flanges 18 and 19, and the ends ofside wall 12 are formed into similar flanges l8 and 19'. The top of front wall 13 is formed into a flange and the top of wall 12 is formed into a flange 21. The junctions of the various flanges on each wall are welded to rigidize the faces of the housing. An angle 17 is welded at its opposite ends to faces 12 and 13 at the bottom of the housing, and an angle 22 is welded at its opposite ends between walls 12 and 13 at the top of the housing. The scroll 25 of a centrifugal fan has its opposite sides secured in airtight relationship, as by welding, between sides 12 and 13 of the housing and an inlet bell 26 is secured, as by screws, to wall 12. The foregoing flange and angle structure provides a rigidity to the housing, and other rigidizing structure also is used as will become apparent hereafter.

In accordance with the present invention, the electric motor 28 which drives fan wheel 29 with blades I4 thereon is mounted on housing door 30 so that when the door 30 is swung open, access may be had to the inside of housing II and to fan wheel 29 without requiring disassembly of the housing or the fan wheel or any of the structure associated therewith. More specifically, motor 28 includes a vertical base 31 which is suitably secured as with bolts (not shown) to vertical base 32 secured to plate 33 (FIG. I) of inverted U-shaped subhousing 33' which also includes a plate 34 in opposition to plate 33 and parallel thereto and a top plate 35 bridging and connected to plates 33 and 34. Motor base 3] is vertically slidable on base 32 to adjust the tension of drive belt 36 consisting of three separate belts which encircle motor pulley 37 and pulley 38 keyed to shaft 39 which is journalled in bearings 40 secured to subhousing top plate 35 and which mounts fan wheel 29 on its opposite end.

Depending on the size of fan 10, the structure mounted on door 30 may vary in weight anywhere from a few hundred pounds to over a thousand pounds. Therefore, if door 30 were mounted only on conventional hinges and used only a latch to secure the door closed, and nothing more, it is quite apparent that the structure could not hold up in use because of the large static forces to which the door would be subjected when it is open and the large dynamic forces to which it would be subjected when closed with the fan running. Therefore, in accordance with the present invention, the door and associated structure on the remainder of the housing are rigidized and effectively tied together so as to permit the fan assembly to withstand the stresses to which it will be subjected both when the fan is in operation with the door closed and when the door is opened. In addition, structure is provided for permitting the door to be opened simply and easily as if it weighed just a few pounds and not the few hundred to a thousand which it actually does weigh.

To achieve the foregoing results, the housing I! includes a base frame section consisting of channel 41 which has its inner end welded to angle 42 which is suitably welded to the bottom of housing wall 13. A second channel 43 (FIG. 3) is welded across sides I2 and 13 and extends beyond side 13 as shown. A third channel 44 has its opposite ends welded to channels 41 and 43. As can be seen, channels 41, 43 and 44 rest firmly on the floor 45 so as to be securely supported thereby.

A suitable frame section is associated with door 30 so as to contribute to the support of the apparatus carried by door 30 both when it is closed and when it is opened. More specifically, angles 46 and 48 are welded to the lower portions of subhousing plates 34 and 33, respec tively, and angle 47 is welded across the outer ends of angles 46 and 48 (FIG. 5). In addition, a rigidizing plate 49 is secured, as by welding, across the inner ends of plates 33 and 34, as is upper plate 50 through which shaft 39 extends. Flanges 51, 52, 53 and 54 are bent outwardly from plate 50 to form the periphery thereof to rigidize it. It can thus be seen that the foregoing structure provides a very rigid door which supports the motor, fan and associated structure.

When the door 30 is closed, the frame angles 46, 47 and 48 rest on the top of channels 41, 44 and 43', respectively, channel 43' having its opposite ends welded to angles 42 and channel 44. Furthermore, fastener bolts 55 and pivotally mounted by clevis connections 56 on channels 41 and 43' so that they can be tightened when in the positions of FIGS. 1, 2, 5 and 6 to cause angles 46 and 48 to be rigidly secured to channels 41 and 43, respectively, that is, to cause the door frame section to be supported rigidly by the housing base frame section. In this respect, it can be seen that fasteners 55 each include a screw portion 57 including a shank 58 which is received in slots, such as 59 of angles 46 and 48, and in corresponding slots 59' of channels 41 and 43.

When it is desired to open door 30 so as to obtain access to the inside of housing II or to fan wheel 29, it is merely necessary to manipulate toggle links 60 by actuating the handles 61 thereof so as to cause the hook portions 62 to be swung out of engaging relationship with holes in angle 63 which is welded to side I3 of the housing. In addition, compression toggles 90 which bear against plate 49 are released. In addition, fastener bolts 55 are loosened and moved from the position of FIG. 6 to assume the position of FIG. 7. Thereafter. screw 64 is turned by rotating handle 67, screw 64 being threaded through the nut 65 welded to the top of plate 35 and also being threaded through nut 66 welded to bracket 66 which is welded to subhousing side plate 34. This will cause screw 64 to travel downwardly and its lower end will bear downwardly on depression 68 (FIG. 6] at one end of lever 69, this end of the lever being slidable between angle brackets 70 and 71 welded to the inside of plate 34. The opposite end of lever 69 is pivotally mounted by pin 72 to angle brackets 73 and 74 (FIG. 5) welded to plate 33. Lever 69 consists of spaced side bars 75 and 76, having a configuration in plan as shown in FIG. 5, with a wheel 77 journalled on shaft 78 extending between plates 75 and 76 at the central portion thereof. As screw 64 moves downwardly, it will bear downwardly on the left end of lever 69 in FIG. 6 and cause wheel 77 to bear downwardly on arcuate track 78 which has one end welded to wall 13 on the housing It and the other end welded to channel 43 (FIG. 3). A continuation 79' of arcuate track 78 has its opposite ends welded between channels 43' and 43. Continued downward movement of screw 64 will cause continued pivotal movement of lever 69 about pivot 72 and this will eventually cause the upward movement of door 30 and all the structure mounted thereon so that their weight is carried by wheel 77 which is in engagement with track 78. Thus. as lever 69 is pivoted downwardly, door 30 will be raised upwardly until such time as wheel 77 supports the entire weight of door 30.

The upward movement of door 30, resulting from the downward movement of screw 64, will be in a vertical rectilinear path as guided by pins 82 ofthe door hinges.

These hinges include the ends of bars 83 and 84 which are welded to door flanges S2 and 54, respectively, and tabs 85 and 86 which are welded to angle 87 (FIG. 4) which in turn is welded to side 13 of the housing, thereby lending rigidity thereto as well as forming the support for the hinges. The foregoing rectilinear motion is permitted by the vertical spacing between tabs 85 and the end of bar 83 and the corresponding spacing on the other hinge between the end of bar 84 and tabs 86. Since the weight of the door, the motor, fan wheel and associated structure are now supported on roller 77, door 30 may be moved from the closed position shown FIGS. 1 and 2 to the open position shown in FIG. 3 with relative ease by merely grasping handle 89 and pulling with a force which should not exceed that reduired for a relatively light door.

After access is no longer desired to the inside of the fan housing with the door 30 in an open position, it is merely required that the door be swung in a clockwise direction in FIG. 3 about its hinges to close it and thereafter screw 64 is backed off so that lever 69 (FIG. 6) will pivot in a clockwise direction about pin 72 until such time as door 30 is lowered so that the frame section on the door, namely, angles 46, 47 and 48, come to rest on the housing frame section, namely, channels 41, 43' and 44. Thereafter locking members 55 are manipulated to the position shown in FIG. 6 to lock the two frame sections securely together after locking handles 60 have been placed in the position shown in FIG. 4 to draw the door up firmly against the fan housing and after toggle levers 90 have been manipulated to cause plate 49 to firmly engage plate wall 13. Furthermore, as can be seen from FIG. 4, a gasket 91 is provided along the edges of door plate 50 to provide a good seal between the door and the remainder of the housing when the door is in the closed position.

Because of the substantial frame section on the door and because of the substantial frame section on the housing, when the two are locked together, the housing and the fan supporting structure will be held firmly against vibration and in the precise position in which they are intended to function. Furthermore, in the event it is desired to obtain access to the inside of the housing, it is merely necessary to follow the above enumerated steps to transfer the weight of the door and the structure carried thereby to the housing frame section so that the door can be rolled open by the roller running on tracks 78 and 79'.

The principles of the invention described above with respect to the embodiment of FIGS. 1-7 are incorporated, with suitable modification, in the embodiment of the invention shown in FIGS. 8-17.

The fan construction 100 is an in-line centrifugal fan including a cylindrical housing or shell 101 having an annular angle 102 welded to the lower end and an annular angle 103 welded to the upper end for rigidizing purposes. An arcuate door 104 has motor 115' and fan wheel 106 and related structure mounted thereon. Door 104 selectively closes opening 105" in shell 101. Door 104 includes an arcuate section 105' to which the longer leg of vertical channel section 105 is welded. Pairs of tabs 106 and 107 are welded in spaced relationship on channel 105 to receive pins 109 which extend through tabs 110 secured to shell 101 and spacedly mounted between tabs 106 and 107, this spacing permitting door 104 to move axially. Thus, channel 105 serves to rigidize door sector 105' and in addition provides a mounting for part of the hinges. A plate 111 includes spaced flanges 112 which are welded to spaced pairs of angles 113 and 114. Angles 113 are welded to channel 105, and angles 114 are welded to channel 115 mounted in parallel spaced relation to channel 105. The base 116 of motor 115 is secured to plate 111 by bolts 117 which permit the vertical adjustment of motor base 116 on plate 111. In addition, bolts 118 extend through angles 113 and 114 and flanges 112 to permit outward horizontal adjustment of plate 111 relative to door sector 105 to effect tensioning of belt 119 which extends around motor pulley 120 and pulley 121 keyed to shaft 122 which mounts fan wheel 106, shaft 122 being mounted in suitable bearings 123 which are mounted on suitable base structure 124 secured to the inside of annular member 125 which is secured to the inside of door sector 105' by hollow tube 126 through which belt 119 extends. In addition. annular member 125 is further secured to door sector 105' by means of air straightening vanes 127 which also rigidize door sector 105'. The motor, fan wheel and related supporting structure are thus rigidly secured to door sector 105'.

A supporting frame section is rigidly secured to housing 101. In this respect, channels 130, 131 and 132 are welded relative to housing 101 to provide a frame as shown in plan in FIG.. 15. Angle members 133 have their oposite ends welded between flnge 102 and channel member 131 for rigidizing purposes. An arcuate track 134 includes a first section 135 (FIG. 11) which is welded between channel 131 and housing shell portion 136 below door 104. A second arcuate track portion 137 has one end welded to channel 131 and the opposite end to one end of strut 138 which in turn has its opposite end welded to shell portion 136.

As can be seen formed FIG. 18, fan wheel 106 has a lower curved portion 140 which lies in overlapping axial relationship with inlet bell 141 secured to plate 142' welded within housing 101 when door 105 is closed, and fan wheel 106 is in operating position. Therefore, before door 104 can be swung to the open position shown in FIG. 15, fan wheel 106 must be lifted so that the lower edge of portion 140 thereof clears the upper edge of inlet bell 141. Accordingly, to effect this lifting, as well as to transfer the weight of door 104 and its appended structure onto the frame on the housing, a lever in the form of angle 143 has one end thereof pivotally secured to channel 105 (FIG. 10) by bolt 144. The vertical leg 143' at the opposite end of lever 143 is slidably confined between web portion 146 of channel 115 and the leg of angle 147 (FIG. 14) which is welded to and extends upwardly from angle 148 secured, as by welding, between channel 115 and angle 175 (FIG. 15), which has its opposite end welded to angle 177 which in turn is welded to channel 105. A screw 149 (FIG. 14) is threaded through a tapped aperture in the horizontal leg 150 of angle 15] which has a vertical leg 152 welded to channel 115 which in turn is welded to door 104. The lower end of screw 149 includes a bearing portion 153 (FIG. 14) which bears on the horizontal leg 154 of lever 143.

When it is desired to open door 104. it is merely necessary to loosen fastener bolts 156 which have a clevis connection at 157 mounted on flange 158 of housing 101 (FIG. 17), flange 158 being a counterpart of rigid izing flange 158. After each screw portion 159 is loosened, it can be swung from the locked position shown in FIG. 17 to the open position shown in FIG. where the head 160 of the fastener will no longer be in engagement with the angle 161 secured, as by welding, to the edge of door sector 105', the shanks 162 of the screws having previously fitted through cutaway porlions 163 in angle 161 (FIG. 12). Thereafter screw 149 is threaded downwardly so that bearing portion 153 bears on the end of lever 143 so as to pivot said lever in a clockwise direction about its pivot pin 144. This will bring wheel 165 (FIGS. 9 and 13), which is journalled between the legs of U-shaped member 166 by pin 167, into firm engagement with the top of track 134. Continued turning of screw 149 downwardly will cause the door 104 to be lifted upwardly as wheel 165 takes the load, and screw 149 is caused to continue downwardly until such time as portion 140 of fan wheel 106 clears above the uppermost rim portion 141 of inlet bell 141 (FIG. 12). Thereafter door 104 can be swung from the closed position shown in FIG. 10 to the open position shown in FIG. 15, with wheel 165 rolling on track 134 to carry the weight ofthe door and all the structure mounted thereon. The upward movement of door 104 is in a rectilinear path, as guided by hinge pins 109.

After access is no longer required to the inside of the fan housing 101, the door can be swung to a closed position so that it seats firmly against gasket 170. After screw 149 is moved upwardly, the load will be removed from wheel 165 so that the frame members on the door will rest firmly on the frame of the housing and portion 140 of the fan wheel and inlet bell 141 will assume the axial overlapping relationship shown in FIG. 18. Fas tener members 156 are then used to tightly close door 104 by moving them to the position of F109 and tightening them. Fastener members 171, which may be identical to fastener members 156, are then swung upwardly to the position shown in FIG. 9 and tightened with the shanks of the screws 172 in cutaway portion 173 of member 131 and in the corresponding cutaway portions 174 in angle member 175 which is secured to channels 105 and 115 by means of angle 177 and 148 (FIG. 10), respectively. At this point it is to be noted that vertical angles 178 and 179 have their lower ends welded to angle 175 and their upper ends welded to angles 113 and 114 whch support plate 111, with the inner ends ofangles 113 and 114 being welded to door 104. When fastener members 171 are moved to the po' sition shown in FIG. 13 and tightened, a very rigid unitized assembly will be obtained whereby the door and all the structure mounted thereon is securely held in position by the frame sections connected to the housing and the door, as described above.

Straightening vanes 180 are located within housing 101 for the purpose of straightening the air flow which fan wheel 106 pumps through housing 101.

It can thus be seen that the improved fan construction of the present invention is manifestly capable of achieving the above enumerated objects and while preferred embodiments of the present invention have been disclosed. it will be understood that the present invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

What is claimed is:

1. A fan construction comprising a fan housing, a door, pivot means pivotally mounting said door on said fan housing, a fan wheel journalled on said door for rotation within said fan housing when said door is closed,

means mounted on said door for driving said fan wheel, a first rigid frame section fixed to said fan housing, a second rigid frame section fixed to said door, fastener means for selectively rigidly securing said first and second rigid frame sections to each other when said door is closed to thereby securely mount said fan and said means for rotating said fan relative to said housing, said means for rotating said fan including motor means, roller means operatively interposed between said first and second rigid frame sections for permitting said second rigid frame section to roll relative to said first rigid frame section during the opening of said door, said roller means comprising a wheel on said second rigid frame section and a track on said first rigid frame section, and means for lifting said second rigid frame section from said first rigid frame section so as to enhance relative movement therebetween during opening of said door.

2. A fan construction as set forth in claim 1 including wheel mounting means for mounting said wheel in a retracted position when said first and second rigid frame sections are secured to each other by said fastener means.

3. A fan construction as set forth in claim 2 wherein said wheel mounting means includes means for bringing said wheel into engagement with said track.

4. A fan construction as set forth in claim 3 wherein said wheel mounting means includes means for simultaneously bringing said wheel into engagement with said track and also raising said second rigid frame section from said first rigid frame section.

5. A fan construction as set forth in claim 4 wherein said wheel mounting means comprises a lever having a first end movably mounted on said second rigid frame section, a second end on said lever pivotally mounted on said second rigid frame section, lever moving means for moving said first end of said lever downwardly, and wherein said wheel is mounted on said lever so that said downward movement of said lever relative to said first rigid frame section effects lifting of said second rigid frame section while simultaneously forcing said wheel into engagement with said track.

6. A fan construction as set forth in claim 5 wherein said lever moving means comprises a screw mounted on said second rigid frame section for exerting a downward force on said first end of said lever.

7. A fan construction as set forth in claim 1 wherein said pivot means guide said door for rectilinear movement during the lifting thereof.

8. A fan construction as set forth in claim 7 wherein said fan housing includes an inlet bell and wherein said fan wheel includes a portion in axial overlapping relationship with said inlet bell when said door is closed and said first and secon frame sections are in engagement with each other whereby the lifting of said second rigid frame section effects an axial movement of said fan wheel relative to said inlet bell to provide clearance therebetween when said door is opened.

9. A fan construction comprising a fan housing. a door, pivot means pivotally mounting said door on said fan housing, a fan wheel journalled on said door for rotation within said fan housing when said door is closed. means mounted on said door for driving said fan wheel. a rigid frame section fixed to said fan housing, fastener means for selectively rigidly securing said door to said housing to thereby securely mount said fan and said means for rotating said fan relative to said housing means for lifting said door relative to said rigid frame section so as to enhance relative movement therebetween during opening of said door. 

1. A fan construction comprising a fan housing, a door, pivot means pivotally mounting said door on said fan housing, a fan wheel journalled on said door for rotation within said fan housing when said door is closed, means mounted on said door for driving said fan wheel, a first rigid frame section fixed to said fan housing, a second rigid frame section fixed to said door, fastener means for selectively rigidly securing said first and second rigid frame sections to each other when said door is closed to thereby securely mount said fan and said means for rotating said fan relative to said housing, said means for rotating said fan including motor means, roller means operatively interposed between said first and second rigid frame sections for permitting said second rigid frame section to roll relative to said first rigid frame section during the opening of said door, said roller means comprising a wheel on said second rigid frame section and a track on said first rigid frame section, and means for lifting said second rigid frame section from said first rigid frame section so as to enhance relative movement therebetween during opening of said door.
 2. A fan construction as set forth in claim 1 including wheel mounting means for mounting said wheel in a retracted position when said first and second rigid frame sections are secured to each other by said fastener means.
 3. A fan construction as set forth in claim 2 wherein said wheel mounting means includes means for bringing said wheel into engagement with said track.
 4. A fan construction as set forth in claim 3 wherein said wheel mounting means includes means for simultaneously bringing said wheel into engagement with said track and also raising said second rigid frame section from said first rigid frame section.
 5. A fan construction as set forth in claim 4 wherein said wheel mounting means comprises a lever having a first end movably mounted on said second rigid frame section, a second end on said lever pivotally mounted on said second rigid frame section, lever moving means for moving said first end of said lever downwardly, and wherein said wheel is mounted on said lever so that said downward movement of said lever relative to said first rigid frame section effects lifting of said second rigid frame section while simultaneously forcing said wheel into engagement with said track.
 6. A fan construction as set forth in claim 5 wherein said lever moving means comprIses a screw mounted on said second rigid frame section for exerting a downward force on said first end of said lever.
 7. A fan construction as set forth in claim 1 wherein said pivot means guide said door for rectilinear movement during the lifting thereof.
 8. A fan construction as set forth in claim 7 wherein said fan housing includes an inlet bell and wherein said fan wheel includes a portion in axial overlapping relationship with said inlet bell when said door is closed and said first and secon frame sections are in engagement with each other whereby the lifting of said second rigid frame section effects an axial movement of said fan wheel relative to said inlet bell to provide clearance therebetween when said door is opened.
 9. A fan construction comprising a fan housing, a door, pivot means pivotally mounting said door on said fan housing, a fan wheel journalled on said door for rotation within said fan housing when said door is closed, means mounted on said door for driving said fan wheel, a rigid frame section fixed to said fan housing, fastener means for selectively rigidly securing said door to said housing to thereby securely mount said fan and said means for rotating said fan relative to said housing when said door is closed, and wheel means operatively interposed between said door and said frame section for permitting said door to roll relative to said rigid frame section during the opening of said door, and means for lifting said door relative to said rigid frame section so as to enhance relative movement therebetween during opening of said door. 